The present invention relates to a master cylinder assembly having a plastic reservoir, and more particularly to the master cylinder assembly with connecting means between a master cylinder housing and the plastic reservoir thereof.
The reservoir tank for containing the working fluid of a hydraulically operated brake system or clutch is generally made of plastic material such as nylon or polythene. The problem arises when the plastic reservoir is fixed to a metallic housing of the master cylinder assembly, because a bottom portion of plastic reservoir is deformed and the sealing between the plastic reservoir and the metallic housing of the master cylinder assembly is not ensured completely.
More particularly, the plastic reservoir tank is conventionally provided with an axial opening through which a bolt is passed so as to screw it into the master cylinder housing. The rotation of the bolt causes the bottom wall of the reservoir to be excessively compressed between a head of the bolt and the master cylinder housing. The rotation of the bolt also causes the seal member interposed between the reservoir and the master cylinder housing to be undesirably compressed. It is hard in practice to get a force proper to tighten the seal member because of the resiliency of the plastic material.
In order to obviate such a difficulty, improvement has been presented, which inserts the metallic washer or gasket into the axial opening of the plastic reservoir.
The above-mentioned improvement is disclosed in U.S. Pat. No. 3,427,807 to Moyes. This prior art is such constructed that the cylindrical sleeve is inserted into the opening in the thickened bottom wall of the reservoir and washer is interposed between a head of the bolt and an inner surface of said bottom wall, thereby preventing the excessive deformation of the bottom wall and making a connection portion of the reservoir and the housing of the master cylinder fluid-tight completely. When the sleeve is located exactly in the opening, the above functions are provided. However, when the sleeve is not fitted in the proper position in said opening, the bottom portion of the reservoir and the rubber seal are undesirably deformed so as not to remain fluid-tight under the usual condition. This means that the prior art is complicate in manufacture.